Synnefo » snf-ganeti » ganeti-local

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# Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Google Inc.

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# General Public License for more details.

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"""Xen hypervisors

"""

import logging

import string # pylint: disable=W0402

from cStringIO import StringIO

from ganeti import constants

from ganeti import errors

from ganeti import utils

from ganeti.hypervisor import hv_base

from ganeti import netutils

from ganeti import objects

from ganeti import pathutils

from ganeti import ssconf

XEND_CONFIG_FILE = utils.PathJoin(pathutils.XEN_CONFIG_DIR, "xend-config.sxp")

XL_CONFIG_FILE = utils.PathJoin(pathutils.XEN_CONFIG_DIR, "xen/xl.conf")

VIF_BRIDGE_SCRIPT = utils.PathJoin(pathutils.XEN_CONFIG_DIR,

                                   "scripts/vif-bridge")

_DOM0_NAME = "Domain-0"

_DISK_LETTERS = string.ascii_lowercase

_FILE_DRIVER_MAP = {

  constants.FD_LOOP: "file",

  constants.FD_BLKTAP: "tap:aio",

  }

def _CreateConfigCpus(cpu_mask):

  """Create a CPU config string for Xen's config file.

  """

  # Convert the string CPU mask to a list of list of int's

  cpu_list = utils.ParseMultiCpuMask(cpu_mask)

  if len(cpu_list) == 1:

    all_cpu_mapping = cpu_list[0]

    if all_cpu_mapping == constants.CPU_PINNING_OFF:

      # If CPU pinning has 1 entry that's "all", then remove the

      # parameter from the config file

      return None

    else:

      # If CPU pinning has one non-all entry, mapping all vCPUS (the entire

      # VM) to one physical CPU, using format 'cpu = "C"'

      return "cpu = \"%s\"" % ",".join(map(str, all_cpu_mapping))

  else:

    def _GetCPUMap(vcpu):

      if vcpu[0] == constants.CPU_PINNING_ALL_VAL:

        cpu_map = constants.CPU_PINNING_ALL_XEN

      else:

        cpu_map = ",".join(map(str, vcpu))

      return "\"%s\"" % cpu_map

    # build the result string in format 'cpus = [ "c", "c", "c" ]',

    # where each c is a physical CPU number, a range, a list, or any

    # combination

    return "cpus = [ %s ]" % ", ".join(map(_GetCPUMap, cpu_list))

def _RunInstanceList(fn, instance_list_errors):

  """Helper function for L{_GetInstanceList} to retrieve the list of instances

  from xen.

  @type fn: callable

  @param fn: Function to query xen for the list of instances

  @type instance_list_errors: list

  @param instance_list_errors: Error list

  @rtype: list

  """

  result = fn()

  if result.failed:

    logging.error("Retrieving the instance list from xen failed (%s): %s",

                  result.fail_reason, result.output)

    instance_list_errors.append(result)

    raise utils.RetryAgain()

  # skip over the heading

  return result.stdout.splitlines()

def _ParseInstanceList(lines, include_node):

  """Parses the output of listing instances by xen.

  @type lines: list

  @param lines: Result of retrieving the instance list from xen

  @type include_node: boolean

  @param include_node: If True, return information for Dom0

  @return: list of tuple containing (name, id, memory, vcpus, state, time

    spent)

  """

  result = []

  # Iterate through all lines while ignoring header

  for line in lines[1:]:

    # The format of lines is:

    # Name      ID Mem(MiB) VCPUs State  Time(s)

    # Domain-0   0  3418     4 r-----    266.2

    data = line.split()

    if len(data) != 6:

      raise errors.HypervisorError("Can't parse instance list,"

                                   " line: %s" % line)

    try:

      data[1] = int(data[1])

      data[2] = int(data[2])

      data[3] = int(data[3])

      data[5] = float(data[5])

    except (TypeError, ValueError), err:

      raise errors.HypervisorError("Can't parse instance list,"

                                   " line: %s, error: %s" % (line, err))

    # skip the Domain-0 (optional)

    if include_node or data[0] != _DOM0_NAME:

      result.append(data)

  return result

def _GetInstanceList(fn, include_node, _timeout=5):

  """Return the list of running instances.

  See L{_RunInstanceList} and L{_ParseInstanceList} for parameter details.

  """

  instance_list_errors = []

  try:

    lines = utils.Retry(_RunInstanceList, (0.3, 1.5, 1.0), _timeout,

                        args=(fn, instance_list_errors))

  except utils.RetryTimeout:

    if instance_list_errors:

      instance_list_result = instance_list_errors.pop()

      errmsg = ("listing instances failed, timeout exceeded (%s): %s" %

                (instance_list_result.fail_reason, instance_list_result.output))

    else:

      errmsg = "listing instances failed"

    raise errors.HypervisorError(errmsg)

  return _ParseInstanceList(lines, include_node)

def _ParseNodeInfo(info):

  """Return information about the node.

  @return: a dict with the following keys (memory values in MiB):

        - memory_total: the total memory size on the node

        - memory_free: the available memory on the node for instances

        - nr_cpus: total number of CPUs

        - nr_nodes: in a NUMA system, the number of domains

        - nr_sockets: the number of physical CPU sockets in the node

        - hv_version: the hypervisor version in the form (major, minor)

  """

  result = {}

  cores_per_socket = threads_per_core = nr_cpus = None

  xen_major, xen_minor = None, None

  memory_total = None

  memory_free = None

  for line in info.splitlines():

    fields = line.split(":", 1)

    if len(fields) < 2:

      continue

    (key, val) = map(lambda s: s.strip(), fields)

    # Note: in Xen 3, memory has changed to total_memory

    if key in ("memory", "total_memory"):

      memory_total = int(val)

    elif key == "free_memory":

      memory_free = int(val)

    elif key == "nr_cpus":

      nr_cpus = result["cpu_total"] = int(val)

    elif key == "nr_nodes":

      result["cpu_nodes"] = int(val)

    elif key == "cores_per_socket":

      cores_per_socket = int(val)

    elif key == "threads_per_core":

      threads_per_core = int(val)

    elif key == "xen_major":

      xen_major = int(val)

    elif key == "xen_minor":

      xen_minor = int(val)

  if None not in [cores_per_socket, threads_per_core, nr_cpus]:

    result["cpu_sockets"] = nr_cpus / (cores_per_socket * threads_per_core)

  if memory_free is not None:

    result["memory_free"] = memory_free

  if memory_total is not None:

    result["memory_total"] = memory_total

  if not (xen_major is None or xen_minor is None):

    result[constants.HV_NODEINFO_KEY_VERSION] = (xen_major, xen_minor)

  return result

def _MergeInstanceInfo(info, instance_list):

  """Updates node information from L{_ParseNodeInfo} with instance info.

  @type info: dict

  @param info: Result from L{_ParseNodeInfo}

  @type instance_list: list of tuples

  @param instance_list: list of instance information; one tuple per instance

  @rtype: dict

  """

  total_instmem = 0

  for (name, _, mem, vcpus, _, _) in instance_list:

    if name == _DOM0_NAME:

      info["memory_dom0"] = mem

      info["dom0_cpus"] = vcpus

    # Include Dom0 in total memory usage

    total_instmem += mem

  memory_free = info.get("memory_free")

  memory_total = info.get("memory_total")

  # Calculate memory used by hypervisor

  if None not in [memory_total, memory_free, total_instmem]:

    info["memory_hv"] = memory_total - memory_free - total_instmem

  return info

def _GetNodeInfo(info, instance_list):

  """Combines L{_MergeInstanceInfo} and L{_ParseNodeInfo}.

  @type instance_list: list of tuples

  @param instance_list: list of instance information; one tuple per instance

  """

  return _MergeInstanceInfo(_ParseNodeInfo(info), instance_list)

def _GetConfigFileDiskData(block_devices, blockdev_prefix,

                           _letters=_DISK_LETTERS):

  """Get disk directives for Xen config file.

  This method builds the xen config disk directive according to the

  given disk_template and block_devices.

  @param block_devices: list of tuples (cfdev, rldev):

      - cfdev: dict containing ganeti config disk part

      - rldev: ganeti.block.bdev.BlockDev object

  @param blockdev_prefix: a string containing blockdevice prefix,

                          e.g. "sd" for /dev/sda

  @return: string containing disk directive for xen instance config file

  """

  if len(block_devices) > len(_letters):

    raise errors.HypervisorError("Too many disks")

  disk_data = []

  for sd_suffix, (cfdev, dev_path) in zip(_letters, block_devices):

    sd_name = blockdev_prefix + sd_suffix

    if cfdev.mode == constants.DISK_RDWR:

      mode = "w"

    else:

      mode = "r"

    if cfdev.dev_type == constants.LD_FILE:

      driver = _FILE_DRIVER_MAP[cfdev.physical_id[0]]

    else:

      driver = "phy"

    disk_data.append("'%s:%s,%s,%s'" % (driver, dev_path, sd_name, mode))

  return disk_data

class XenHypervisor(hv_base.BaseHypervisor):

  """Xen generic hypervisor interface

  This is the Xen base class used for both Xen PVM and HVM. It contains

  all the functionality that is identical for both.

  """

  CAN_MIGRATE = True

  REBOOT_RETRY_COUNT = 60

  REBOOT_RETRY_INTERVAL = 10

  ANCILLARY_FILES = [

    XEND_CONFIG_FILE,

    XL_CONFIG_FILE,

    VIF_BRIDGE_SCRIPT,

    ]

  ANCILLARY_FILES_OPT = [

    XL_CONFIG_FILE,

    ]

  def __init__(self, _cfgdir=None, _run_cmd_fn=None, _cmd=None):

    hv_base.BaseHypervisor.__init__(self)

    if _cfgdir is None:

      self._cfgdir = pathutils.XEN_CONFIG_DIR

    else:

      self._cfgdir = _cfgdir

    if _run_cmd_fn is None:

      self._run_cmd_fn = utils.RunCmd

    else:

      self._run_cmd_fn = _run_cmd_fn

    self._cmd = _cmd

  def _GetCommand(self, hvparams):

    """Returns Xen command to use.

    @type hvparams: dict of strings

    @param hvparams: hypervisor parameters

    """

    if self._cmd is None:

      if hvparams is None or constants.HV_XEN_CMD not in hvparams:

        raise errors.HypervisorError("Cannot determine xen command.")

      else:

        cmd = hvparams[constants.HV_XEN_CMD]

    else:

      cmd = self._cmd

    if cmd not in constants.KNOWN_XEN_COMMANDS:

      raise errors.ProgrammerError("Unknown Xen command '%s'" % cmd)

    return cmd

  def _RunXen(self, args, hvparams):

    """Wrapper around L{utils.process.RunCmd} to run Xen command.

    @type hvparams: dict of strings

    @param hvparams: dictionary of hypervisor params

    @see: L{utils.process.RunCmd}

    """

    cmd = [self._GetCommand(hvparams)]

    cmd.extend(args)

    return self._run_cmd_fn(cmd)

  def _ConfigFileName(self, instance_name):

    """Get the config file name for an instance.

    @param instance_name: instance name

    @type instance_name: str

    @return: fully qualified path to instance config file

    @rtype: str

    """

    return utils.PathJoin(self._cfgdir, instance_name)

  @classmethod

  def _GetConfig(cls, instance, startup_memory, block_devices):

    """Build Xen configuration for an instance.

    """

    raise NotImplementedError

  def _WriteConfigFile(self, instance_name, data):

    """Write the Xen config file for the instance.

    This version of the function just writes the config file from static data.

    """

    # just in case it exists

    utils.RemoveFile(utils.PathJoin(self._cfgdir, "auto", instance_name))

    cfg_file = self._ConfigFileName(instance_name)

    try:

      utils.WriteFile(cfg_file, data=data)

    except EnvironmentError, err:

      raise errors.HypervisorError("Cannot write Xen instance configuration"

                                   " file %s: %s" % (cfg_file, err))

  def _ReadConfigFile(self, instance_name):

    """Returns the contents of the instance config file.

    """

    filename = self._ConfigFileName(instance_name)

    try:

      file_content = utils.ReadFile(filename)

    except EnvironmentError, err:

      raise errors.HypervisorError("Failed to load Xen config file: %s" % err)

    return file_content

  def _RemoveConfigFile(self, instance_name):

    """Remove the xen configuration file.

    """

    utils.RemoveFile(self._ConfigFileName(instance_name))

  def _StashConfigFile(self, instance_name):

    """Move the Xen config file to the log directory and return its new path.

    """

    old_filename = self._ConfigFileName(instance_name)

    base = ("%s-%s" %

            (instance_name, utils.TimestampForFilename()))

    new_filename = utils.PathJoin(pathutils.LOG_XEN_DIR, base)

    utils.RenameFile(old_filename, new_filename)

    return new_filename

  def _GetInstanceList(self, include_node, hvparams):

    """Wrapper around module level L{_GetInstanceList}.

    @type hvparams: dict of strings

    @param hvparams: hypervisor parameters to be used on this node

    """

    return _GetInstanceList(lambda: self._RunXen(["list"], hvparams),

                            include_node)

  def ListInstances(self, hvparams=None):

    """Get the list of running instances.

    """

    instance_list = self._GetInstanceList(False, hvparams)

    names = [info[0] for info in instance_list]

    return names

  def GetInstanceInfo(self, instance_name, hvparams=None):

    """Get instance properties.

    @type instance_name: string

    @param instance_name: the instance name

    @type hvparams: dict of strings

    @param hvparams: the instance's hypervisor params

    @return: tuple (name, id, memory, vcpus, stat, times)

    """

    instance_list = self._GetInstanceList(instance_name == _DOM0_NAME, hvparams)

    result = None

    for data in instance_list:

      if data[0] == instance_name:

        result = data

        break

    return result

  def GetAllInstancesInfo(self, hvparams=None):

    """Get properties of all instances.

    @type hvparams: dict of strings

    @param hvparams: hypervisor parameters

    @return: list of tuples (name, id, memory, vcpus, stat, times)

    """

    return self._GetInstanceList(False, hvparams)

  def _MakeConfigFile(self, instance, startup_memory, block_devices):

    """Gather configuration details and write to disk.

    See L{_GetConfig} for arguments.

    """

    buf = StringIO()

    buf.write("# Automatically generated by Ganeti. Do not edit!\n")

    buf.write("\n")

    buf.write(self._GetConfig(instance, startup_memory, block_devices))

    buf.write("\n")

    self._WriteConfigFile(instance.name, buf.getvalue())

  def StartInstance(self, instance, block_devices, startup_paused):

    """Start an instance.

    """

    startup_memory = self._InstanceStartupMemory(instance,

                                                 hvparams=instance.hvparams)

    self._MakeConfigFile(instance, startup_memory, block_devices)

    cmd = ["create"]

    if startup_paused:

      cmd.append("-p")

    cmd.append(self._ConfigFileName(instance.name))

    result = self._RunXen(cmd, instance.hvparams)

    if result.failed:

      # Move the Xen configuration file to the log directory to avoid

      # leaving a stale config file behind.

      stashed_config = self._StashConfigFile(instance.name)

      raise errors.HypervisorError("Failed to start instance %s: %s (%s). Moved"

                                   " config file to %s" %

                                   (instance.name, result.fail_reason,

                                    result.output, stashed_config))

  def StopInstance(self, instance, force=False, retry=False, name=None):

    """Stop an instance.

    """

    if name is None:

      name = instance.name

    return self._StopInstance(name, force, instance.hvparams)

  def _StopInstance(self, name, force, hvparams):

    """Stop an instance.

    @type name: string

    @param name: name of the instance to be shutdown

    @type force: boolean

    @param force: flag specifying whether shutdown should be forced

    @type hvparams: dict of string

    @param hvparams: hypervisor parameters of the instance

    """

    if force:

      action = "destroy"

    else:

      action = "shutdown"

    result = self._RunXen([action, name], hvparams)

    if result.failed:

      raise errors.HypervisorError("Failed to stop instance %s: %s, %s" %

                                   (name, result.fail_reason, result.output))

    # Remove configuration file if stopping/starting instance was successful

    self._RemoveConfigFile(name)

  def RebootInstance(self, instance):

    """Reboot an instance.

    """

    ini_info = self.GetInstanceInfo(instance.name, hvparams=instance.hvparams)

    if ini_info is None:

      raise errors.HypervisorError("Failed to reboot instance %s,"

                                   " not running" % instance.name)

    result = self._RunXen(["reboot", instance.name], instance.hvparams)

    if result.failed:

      raise errors.HypervisorError("Failed to reboot instance %s: %s, %s" %

                                   (instance.name, result.fail_reason,

                                    result.output))

    def _CheckInstance():

      new_info = self.GetInstanceInfo(instance.name, hvparams=instance.hvparams)

      # check if the domain ID has changed or the run time has decreased

      if (new_info is not None and

          (new_info[1] != ini_info[1] or new_info[5] < ini_info[5])):

        return

      raise utils.RetryAgain()

    try:

      utils.Retry(_CheckInstance, self.REBOOT_RETRY_INTERVAL,

                  self.REBOOT_RETRY_INTERVAL * self.REBOOT_RETRY_COUNT)

    except utils.RetryTimeout:

      raise errors.HypervisorError("Failed to reboot instance %s: instance"

                                   " did not reboot in the expected interval" %

                                   (instance.name, ))

  def BalloonInstanceMemory(self, instance, mem):

    """Balloon an instance memory to a certain value.

    @type instance: L{objects.Instance}

    @param instance: instance to be accepted

    @type mem: int

    @param mem: actual memory size to use for instance runtime

    """

    result = self._RunXen(["mem-set", instance.name, mem], instance.hvparams)

    if result.failed:

      raise errors.HypervisorError("Failed to balloon instance %s: %s (%s)" %

                                   (instance.name, result.fail_reason,

                                    result.output))

    # Update configuration file

    cmd = ["sed", "-ie", "s/^memory.*$/memory = %s/" % mem]

    cmd.append(self._ConfigFileName(instance.name))

    result = utils.RunCmd(cmd)

    if result.failed:

      raise errors.HypervisorError("Failed to update memory for %s: %s (%s)" %

                                   (instance.name, result.fail_reason,

                                    result.output))

  def GetNodeInfo(self, hvparams=None):

    """Return information about the node.

    @see: L{_GetNodeInfo} and L{_ParseNodeInfo}

    """

    result = self._RunXen(["info"], hvparams)

    if result.failed:

      logging.error("Can't retrieve xen hypervisor information (%s): %s",

                    result.fail_reason, result.output)

      return None

    instance_list = self._GetInstanceList(True, hvparams)

    return _GetNodeInfo(result.stdout, instance_list)

  @classmethod

  def GetInstanceConsole(cls, instance, hvparams, beparams):

    """Return a command for connecting to the console of an instance.

    """

    return objects.InstanceConsole(instance=instance.name,

                                   kind=constants.CONS_SSH,

                                   host=instance.primary_node,

                                   user=constants.SSH_CONSOLE_USER,

                                   command=[pathutils.XEN_CONSOLE_WRAPPER,

                                            constants.XEN_CMD, instance.name])

  def Verify(self, hvparams=None):

    """Verify the hypervisor.

    For Xen, this verifies that the xend process is running.

    @type hvparams: dict of strings

    @param hvparams: hypervisor parameters to be verified against

    @return: Problem description if something is wrong, C{None} otherwise

    """

    if hvparams is None:

      return "Could not verify the hypervisor, because no hvparams were" \

             " provided."

    if constants.HV_XEN_CMD in hvparams:

      xen_cmd = hvparams[constants.HV_XEN_CMD]

      try:

        self._CheckToolstack(xen_cmd)

      except errors.HypervisorError:

        return "The configured xen toolstack '%s' is not available on this" \

               " node." % xen_cmd

    result = self._RunXen(["info"], hvparams)

    if result.failed:

      return "Retrieving information from xen failed: %s, %s" % \

        (result.fail_reason, result.output)

    return None

  def MigrationInfo(self, instance):

    """Get instance information to perform a migration.

    @type instance: L{objects.Instance}

    @param instance: instance to be migrated

    @rtype: string

    @return: content of the xen config file

    """

    return self._ReadConfigFile(instance.name)

  def AcceptInstance(self, instance, info, target):

    """Prepare to accept an instance.

    @type instance: L{objects.Instance}

    @param instance: instance to be accepted

    @type info: string

    @param info: content of the xen config file on the source node

    @type target: string

    @param target: target host (usually ip), on this node

    """

    pass

  def FinalizeMigrationDst(self, instance, info, success):

    """Finalize an instance migration.

    After a successful migration we write the xen config file.

    We do nothing on a failure, as we did not change anything at accept time.

    @type instance: L{objects.Instance}

    @param instance: instance whose migration is being finalized

    @type info: string

    @param info: content of the xen config file on the source node

    @type success: boolean

    @param success: whether the migration was a success or a failure

    """

    if success:

      self._WriteConfigFile(instance.name, info)

  def MigrateInstance(self, instance, target, live):

    """Migrate an instance to a target node.

    The migration will not be attempted if the instance is not

    currently running.

    @type instance: L{objects.Instance}

    @param instance: the instance to be migrated

    @type target: string

    @param target: ip address of the target node

    @type live: boolean

    @param live: perform a live migration

    """

    port = instance.hvparams[constants.HV_MIGRATION_PORT]

    # TODO: Pass cluster name via RPC

    cluster_name = ssconf.SimpleStore().GetClusterName()

    return self._MigrateInstance(cluster_name, instance.name, target, port,

                                 live, instance.hvparams)

  def _MigrateInstance(self, cluster_name, instance_name, target, port, live,

                       hvparams, _ping_fn=netutils.TcpPing):

    """Migrate an instance to a target node.

    @see: L{MigrateInstance} for details

    """

    if hvparams is None:

      raise errors.HypervisorError("No hvparams provided.")

    if self.GetInstanceInfo(instance_name, hvparams=hvparams) is None:

      raise errors.HypervisorError("Instance not running, cannot migrate")

    cmd = self._GetCommand(hvparams)

    if (cmd == constants.XEN_CMD_XM and

        not _ping_fn(target, port, live_port_needed=True)):

      raise errors.HypervisorError("Remote host %s not listening on port"

                                   " %s, cannot migrate" % (target, port))

    args = ["migrate"]

    if cmd == constants.XEN_CMD_XM:

      args.extend(["-p", "%d" % port])

      if live:

        args.append("-l")

    elif cmd == constants.XEN_CMD_XL:

      args.extend([

        "-s", constants.XL_SSH_CMD % cluster_name,

        "-C", self._ConfigFileName(instance_name),

        ])

    else:

      raise errors.HypervisorError("Unsupported Xen command: %s" % self._cmd)

    args.extend([instance_name, target])

    result = self._RunXen(args, hvparams)

    if result.failed:

      raise errors.HypervisorError("Failed to migrate instance %s: %s" %

                                   (instance_name, result.output))

  def FinalizeMigrationSource(self, instance, success, live):

    """Finalize the instance migration on the source node.

    @type instance: L{objects.Instance}

    @param instance: the instance that was migrated

    @type success: bool

    @param success: whether the migration succeeded or not

    @type live: bool

    @param live: whether the user requested a live migration or not

    """

    # pylint: disable=W0613

    if success:

      # remove old xen file after migration succeeded

      try:

        self._RemoveConfigFile(instance.name)

      except EnvironmentError:

        logging.exception("Failure while removing instance config file")

  def GetMigrationStatus(self, instance):

    """Get the migration status

    As MigrateInstance for Xen is still blocking, if this method is called it

    means that MigrateInstance has completed successfully. So we can safely

    assume that the migration was successful and notify this fact to the client.

    @type instance: L{objects.Instance}

    @param instance: the instance that is being migrated

    @rtype: L{objects.MigrationStatus}

    @return: the status of the current migration (one of

             L{constants.HV_MIGRATION_VALID_STATUSES}), plus any additional

             progress info that can be retrieved from the hypervisor

    """

    return objects.MigrationStatus(status=constants.HV_MIGRATION_COMPLETED)

  @classmethod

  def PowercycleNode(cls):

    """Xen-specific powercycle.

    This first does a Linux reboot (which triggers automatically a Xen

    reboot), and if that fails it tries to do a Xen reboot. The reason

    we don't try a Xen reboot first is that the xen reboot launches an

    external command which connects to the Xen hypervisor, and that

    won't work in case the root filesystem is broken and/or the xend

    daemon is not working.

    """

    try:

      cls.LinuxPowercycle()

    finally:

      utils.RunCmd([constants.XEN_CMD, "debug", "R"])

  def _CheckToolstack(self, xen_cmd):

    """Check whether the given toolstack is available on the node.

    @type xen_cmd: string

    @param xen_cmd: xen command (e.g. 'xm' or 'xl')

    """

    binary_found = self._CheckToolstackBinary(xen_cmd)

    if not binary_found:

      raise errors.HypervisorError("No '%s' binary found on node." % xen_cmd)

    elif xen_cmd == constants.XEN_CMD_XL:

      if not self._CheckToolstackXlConfigured():

        raise errors.HypervisorError("Toolstack '%s' is not enabled on this"

                                     "node." % xen_cmd)

  def _CheckToolstackBinary(self, xen_cmd):

    """Checks whether the xen command's binary is found on the machine.

    """

    if xen_cmd not in constants.KNOWN_XEN_COMMANDS:

      raise errors.HypervisorError("Unknown xen command '%s'." % xen_cmd)

    result = self._run_cmd_fn(["which", xen_cmd])

    return not result.failed

  def _CheckToolstackXlConfigured(self):

    """Checks whether xl is enabled on an xl-capable node.

    @rtype: bool

    @returns: C{True} if 'xl' is enabled, C{False} otherwise

    """

    result = self._run_cmd_fn([constants.XEN_CMD_XL, "help"])

    if not result.failed:

      return True

    elif result.failed:

      if "toolstack" in result.stderr:

        return False

      # xl fails for some other reason than the toolstack

      else:

        raise errors.HypervisorError("Cannot run xen ('%s'). Error: %s."

                                     % (constants.XEN_CMD_XL, result.stderr))

class XenPvmHypervisor(XenHypervisor):

  """Xen PVM hypervisor interface"""

  PARAMETERS = {

    constants.HV_USE_BOOTLOADER: hv_base.NO_CHECK,

    constants.HV_BOOTLOADER_PATH: hv_base.OPT_FILE_CHECK,

    constants.HV_BOOTLOADER_ARGS: hv_base.NO_CHECK,

    constants.HV_KERNEL_PATH: hv_base.REQ_FILE_CHECK,

    constants.HV_INITRD_PATH: hv_base.OPT_FILE_CHECK,

    constants.HV_ROOT_PATH: hv_base.NO_CHECK,

    constants.HV_KERNEL_ARGS: hv_base.NO_CHECK,

    constants.HV_MIGRATION_PORT: hv_base.REQ_NET_PORT_CHECK,

    constants.HV_MIGRATION_MODE: hv_base.MIGRATION_MODE_CHECK,

    # TODO: Add a check for the blockdev prefix (matching [a-z:] or similar).

    constants.HV_BLOCKDEV_PREFIX: hv_base.NO_CHECK,

    constants.HV_REBOOT_BEHAVIOR:

      hv_base.ParamInSet(True, constants.REBOOT_BEHAVIORS),

    constants.HV_CPU_MASK: hv_base.OPT_MULTI_CPU_MASK_CHECK,

    constants.HV_CPU_CAP: hv_base.OPT_NONNEGATIVE_INT_CHECK,

    constants.HV_CPU_WEIGHT:

      (False, lambda x: 0 < x < 65536, "invalid weight", None, None),

    constants.HV_XEN_CMD:

      hv_base.ParamInSet(True, constants.KNOWN_XEN_COMMANDS),

    }

  def _GetConfig(self, instance, startup_memory, block_devices):

    """Write the Xen config file for the instance.

    """

    hvp = instance.hvparams

    config = StringIO()

    config.write("# this is autogenerated by Ganeti, please do not edit\n#\n")

    # if bootloader is True, use bootloader instead of kernel and ramdisk

    # parameters.

    if hvp[constants.HV_USE_BOOTLOADER]:

      # bootloader handling

      bootloader_path = hvp[constants.HV_BOOTLOADER_PATH]

      if bootloader_path:

        config.write("bootloader = '%s'\n" % bootloader_path)

      else:

        raise errors.HypervisorError("Bootloader enabled, but missing"

                                     " bootloader path")

      bootloader_args = hvp[constants.HV_BOOTLOADER_ARGS]

      if bootloader_args:

        config.write("bootargs = '%s'\n" % bootloader_args)

    else:

      # kernel handling

      kpath = hvp[constants.HV_KERNEL_PATH]

      config.write("kernel = '%s'\n" % kpath)

      # initrd handling

      initrd_path = hvp[constants.HV_INITRD_PATH]

      if initrd_path:

        config.write("ramdisk = '%s'\n" % initrd_path)

    # rest of the settings

    config.write("memory = %d\n" % startup_memory)

    config.write("maxmem = %d\n" % instance.beparams[constants.BE_MAXMEM])

    config.write("vcpus = %d\n" % instance.beparams[constants.BE_VCPUS])

    cpu_pinning = _CreateConfigCpus(hvp[constants.HV_CPU_MASK])

    if cpu_pinning:

      config.write("%s\n" % cpu_pinning)

    cpu_cap = hvp[constants.HV_CPU_CAP]

    if cpu_cap:

      config.write("cpu_cap=%d\n" % cpu_cap)

    cpu_weight = hvp[constants.HV_CPU_WEIGHT]

    if cpu_weight:

      config.write("cpu_weight=%d\n" % cpu_weight)

    config.write("name = '%s'\n" % instance.name)

    vif_data = []

    for nic in instance.nics:

      nic_str = "mac=%s" % (nic.mac)

      ip = getattr(nic, "ip", None)

      if ip is not None:

        nic_str += ", ip=%s" % ip

      if nic.nicparams[constants.NIC_MODE] == constants.NIC_MODE_BRIDGED:

        nic_str += ", bridge=%s" % nic.nicparams[constants.NIC_LINK]

      vif_data.append("'%s'" % nic_str)

    disk_data = \

      _GetConfigFileDiskData(block_devices, hvp[constants.HV_BLOCKDEV_PREFIX])

    config.write("vif = [%s]\n" % ",".join(vif_data))

    config.write("disk = [%s]\n" % ",".join(disk_data))

    if hvp[constants.HV_ROOT_PATH]:

      config.write("root = '%s'\n" % hvp[constants.HV_ROOT_PATH])

    config.write("on_poweroff = 'destroy'\n")

    if hvp[constants.HV_REBOOT_BEHAVIOR] == constants.INSTANCE_REBOOT_ALLOWED:

      config.write("on_reboot = 'restart'\n")

    else:

      config.write("on_reboot = 'destroy'\n")

    config.write("on_crash = 'restart'\n")

    config.write("extra = '%s'\n" % hvp[constants.HV_KERNEL_ARGS])

    return config.getvalue()

class XenHvmHypervisor(XenHypervisor):

  """Xen HVM hypervisor interface"""

  ANCILLARY_FILES = XenHypervisor.ANCILLARY_FILES + [

    pathutils.VNC_PASSWORD_FILE,

    ]

  ANCILLARY_FILES_OPT = XenHypervisor.ANCILLARY_FILES_OPT + [

    pathutils.VNC_PASSWORD_FILE,

    ]

  PARAMETERS = {

    constants.HV_ACPI: hv_base.NO_CHECK,

    constants.HV_BOOT_ORDER: (True, ) +

      (lambda x: x and len(x.strip("acdn")) == 0,

       "Invalid boot order specified, must be one or more of [acdn]",

       None, None),

    constants.HV_CDROM_IMAGE_PATH: hv_base.OPT_FILE_CHECK,

    constants.HV_DISK_TYPE:

      hv_base.ParamInSet(True, constants.HT_HVM_VALID_DISK_TYPES),

    constants.HV_NIC_TYPE:

      hv_base.ParamInSet(True, constants.HT_HVM_VALID_NIC_TYPES),

    constants.HV_PAE: hv_base.NO_CHECK,

    constants.HV_VNC_BIND_ADDRESS:

      (False, netutils.IP4Address.IsValid,

       "VNC bind address is not a valid IP address", None, None),

    constants.HV_KERNEL_PATH: hv_base.REQ_FILE_CHECK,

    constants.HV_DEVICE_MODEL: hv_base.REQ_FILE_CHECK,

    constants.HV_VNC_PASSWORD_FILE: hv_base.REQ_FILE_CHECK,

    constants.HV_MIGRATION_PORT: hv_base.REQ_NET_PORT_CHECK,

    constants.HV_MIGRATION_MODE: hv_base.MIGRATION_MODE_CHECK,

    constants.HV_USE_LOCALTIME: hv_base.NO_CHECK,

    # TODO: Add a check for the blockdev prefix (matching [a-z:] or similar).

    constants.HV_BLOCKDEV_PREFIX: hv_base.NO_CHECK,

    # Add PCI passthrough

    constants.HV_PASSTHROUGH: hv_base.NO_CHECK,

    constants.HV_REBOOT_BEHAVIOR:

      hv_base.ParamInSet(True, constants.REBOOT_BEHAVIORS),

    constants.HV_CPU_MASK: hv_base.OPT_MULTI_CPU_MASK_CHECK,

    constants.HV_CPU_CAP: hv_base.NO_CHECK,

    constants.HV_CPU_WEIGHT:

      (False, lambda x: 0 < x < 65535, "invalid weight", None, None),

    constants.HV_VIF_TYPE:

      hv_base.ParamInSet(False, constants.HT_HVM_VALID_VIF_TYPES),

    constants.HV_XEN_CMD:

      hv_base.ParamInSet(True, constants.KNOWN_XEN_COMMANDS),

    }

  def _GetConfig(self, instance, startup_memory, block_devices):

    """Create a Xen 3.1 HVM config file.

    """

    hvp = instance.hvparams

    config = StringIO()

    # kernel handling

    kpath = hvp[constants.HV_KERNEL_PATH]

    config.write("kernel = '%s'\n" % kpath)

    config.write("builder = 'hvm'\n")

    config.write("memory = %d\n" % startup_memory)

    config.write("maxmem = %d\n" % instance.beparams[constants.BE_MAXMEM])

    config.write("vcpus = %d\n" % instance.beparams[constants.BE_VCPUS])

    cpu_pinning = _CreateConfigCpus(hvp[constants.HV_CPU_MASK])

    if cpu_pinning:

      config.write("%s\n" % cpu_pinning)

    cpu_cap = hvp[constants.HV_CPU_CAP]

    if cpu_cap:

      config.write("cpu_cap=%d\n" % cpu_cap)

    cpu_weight = hvp[constants.HV_CPU_WEIGHT]

    if cpu_weight:

      config.write("cpu_weight=%d\n" % cpu_weight)

    config.write("name = '%s'\n" % instance.name)

    if hvp[constants.HV_PAE]:

      config.write("pae = 1\n")

    else:

      config.write("pae = 0\n")

    if hvp[constants.HV_ACPI]:

      config.write("acpi = 1\n")

    else:

      config.write("acpi = 0\n")

    config.write("apic = 1\n")

    config.write("device_model = '%s'\n" % hvp[constants.HV_DEVICE_MODEL])

    config.write("boot = '%s'\n" % hvp[constants.HV_BOOT_ORDER])

    config.write("sdl = 0\n")

    config.write("usb = 1\n")

    config.write("usbdevice = 'tablet'\n")

    config.write("vnc = 1\n")